I do love Iris. In an early story of mine that I wrote, I had a spunky little girl named that, so personally I don't think it old lady. The younger generation (about ages 8 and under) knows it through the latest Pokémon game (the character is a purple haired Gym Leader/Champion), so I doubt any kids will laugh about it being old fashioned.

Here are some awesome middles to pair with it that make it seem more modern: